The effect of temperature on the survival, growth, photosynthesis, and respiration of young seedlings of eelgrass Zostera marina L.

Abstract

The effects of constant temperatures (10, 15, 20, 25, and 30°C) and fluctuating temperatures (10±2, 15±2, 20±2, 25±2, and 30±2°C) on the survival, growth, photosynthesis, and respiration of young eelgrass seedlings were tested under controlled laboratory conditions. The seedling survival rates were not significantly affected (P>0.05) by temperature. The relationship between leaf length, leaf width, sheath length, or root length and constant temperature could be expressed as a quadratic equation using curve estimation. The estimated maximum leaf length, leaf width, sheath length, and root length were achieved at 16.9, 17.2, 16.2, and 16.0°C, respectively. Young seedlings under the 15±2°C treatment had significantly higher leaf length, leaf width, sheath length, and root length compared with those under other treatments (P<0.05). Seedling growth was inhibited by higher temperature (30°C or 30±2°C). The highest photosynthetic rate (0.35±0.05 and 0.43±0.03mgO2g−1h−1, respectively) was attained at 20 and 15±2°C, respectively. However, young seedlings under the 25 and 25±2°C treatments had significantly greater respiratory rates than those under other treatments (P<0.01). Temperature negatively affects the photosynthetic pigment content, with these values dropping sharply at 25 and 25±2°C (P<0.05). However, the chlorophyll a:b ratio was not significantly affected by temperature (P>0.05). The average survival rate, morphologic parameter, photosynthetic rate, respiratory rate, and photosynthetic pigment content of seedlings under the fluctuating temperature treatments were higher than those of seedlings under the constant temperature treatments. However, no significant difference (P>0.05) was found between different treatments. These results indicate that the optimum temperature range for young Z. marina seedling growth is 16–17°C, and temperature fluctuations promote the development and growth of seedlings. The findings are beneficial for developing successful restoration techniques involving early life stages of seagrasses.